Open the My Games tab in Impulse, does it show up there as available? If it does, you can just download it (make sure you uninstall Sins first and re-install to be safe).

If it doesn't, things to try:

a ) Hit F5 to refresh

b ) Restart Impulse

c ) Go to blue orb > register a product and check to see if Sins shows up in the list.

   - If it doesn't, check your email and make sure the serial was sent to the same e-mail addy you're using to log in. If it's a different one, you'll have to contact support@stardock.com to merge emails.

Top left corner in Impulse, the one with the Stardock logo

Several people seem to be having this issue (including myself)

The blue orb Annatar 11 suggested should work and allow access to the download, however you first need the confirmation e-mail which provides the registration code.

I know their customer service does not operate over weekends, they don't seem to be sending out automatic e-mails either - although they seem to have no problems taking money over that period

They give no warning to suggest that they will not provide registrations over weekends, but all we can do is hope it gets resolved in the week.